Hydraulic pump or motor



March 29, 1966 v. BUSH HYDRAULIC PUMP OR MOTOR 6 Sheets-Sheet 1 OriginalFiled Oct. 6, 1961 Ash/5197a? March 29, 1966 v. BUSH HYDRAULIC PUMP ORMOTOR 6 Sh eecs-Sheet '2 Original Filed Oct. 6, 1961 March 29, 1966 v.BUSH 3,242,870

HYDRAULIC PUMP 0 R MOTOR Original Filed Oct. 6, 1961 6 SheetswSheet SMarch 29, 1966 v. BUSH HYDRAULIC PUMP OR MOTOR 5 Sheets-Sheet 4 OriginalFiled Oct. 6, 1961 w Mi? Vaaaerar '50.;6-

March 29, 1966 v. BUSH 3,242,870

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March 29, 1966 v. BUSH HYDRAULIC PUMP 0R MOTOR 6 Sheets-Sheet 6 OriginalFiled Oct. 6, 1961 0 a m Q i Y Z T N & 5r a NW f n 0 h a 8 m &

f G n ja 1- 4 x M1 w H I). a I w a i k 0 n A //arne/ United StatesPatent 3,242,870 HYDRAULIC PUMP OR MOTOR Vannevar Bush, Belmont, Mass.,assignor to Stewart- Warner Corporation, Chicago, Ill., a corporation ofVirginia Original application Oct. 6, 1961, Ser. No. 143,476, now PatentNo. 3,211,107, dated Oct. 12, 1965. Divided and this application Apr. 9,1965, Ser. No. 446,958 4 Claims. (Cl. 163-174) This application is adivision of application Serial No. 143,476, filed October 6, 1961, nowPatent No. 3,211,107, issued October 12, 1965, and relates to highpressure bydraulic units, and more particularly to hydraulic pump ormotor units of the radial piston type having one or more variable volumechambers.

One device of this general type includes a housing, a rotatableeccentric, and two mating members movable relative to one another todefine each variable volume chamber. The first member reciprocatestransversely of the housing while the second member moves on theeccentric in a circular path relative to the housing without rotatingabout its own axis. Relative reciprocation of the members varies thevolume of the chamber and causes a torque about the eccentric mountingto convert between mechanical energy and fluid pressure energy. Inletand outlet means alternately respond to movement of the members forcommunicating a working fluid to and from each chamber.

A major limitation of existing hydraulic units is the presence ofsurfaces which slide upon one another while being pressed together withforces per unit area that can be enormously greater than the fluidpressure. The sliding surfaces must be separated from each other by alubricating film of fluid regardless of the magnitude of the forcespressing the surfaces together. If the supporting film is destroyed,metal-to-metal contact will occur and the life of the unit will begreatly reduced. The use of a high-viscosity lubricating fluid, whichcannot be readily squeezed out from between the surfaces, isimpracticable because there would be excessive losses due to fluidfriction. Thus, for maximum success, the lubricating film must have aload carrying capacity which increases proportionally to the biasingforces, or the pressure of the working fluid.

A second major limitaton of existing hydraulic units is the presence ofcouples, or cocking moments, between mating members such as between thepiston and cylinder and/ or between either the piston or cylinder andits adjacent reaction member. These couples are caused by the manner inwhich reaction torque is transmitted to the machine. The parts arearranged so that the fluid pressure exerts an axial force on the pistonmoving in the cylinder. The force is absorbed by the reaction membersacting on a moment arm to produce a torque about the center of themachine. The reaction torque must be transmitted from one opposingreaction member of the machine through the piston and cylinder to theother opposing reaction member. Because of the arrangement of parts,there is a couple, or cocking moment, set up which causes the parts tobe tilted with respect to each other. The moment arm of a particularcouple may be very small, resulting in the application of extremelylarge forces. Moreover, due to the tilting, these large forces areapplied over a very small area approaching line contact instead. of areacontact. These large forces and small or negligible areas result inenormously large forces per unit area, or pressures, which cannot besupported by an oil film. Metal-to-rnetal contact will then occur. Thus,it is desirable in a dependable hydraulic machine to eliminate all suchcouples.

Another limitation to full success of any hydraulic unit is leakage ofthe working fluid past the mating parts from the high pressure region orchamber to the low pressure region. Leakage is an importantconsideration since the amount of leakage is proportional to the fluidpressure. When the fluid pressure is low the volume of fluid leaked isgenerally small compared to the active volume of the high pressureregion. But, as the pressure is increased, the fractional part of theworking fluid that leaks rises, and at very high pressures it can becomeintolerable. Consequently, a high pressure hydraulic unit must have highresistance leakage paths past the mating parts between the high and lowpressure regions.

Another limitation and potential problem of high pressure hydraulicunits is porting the working fluid to and from each chamber. Generally,the chamber Wall has a port that is covered and uncovered by a movablemember supported on a lubricating film adjacent the wall. As the port isopened, high and low pressure regions are connected resulting in fluidflow through the port and possible displacement of the member intodirect engagement with the Wall. To minimize this condition it isdesirable to port the chamber symmetrically of the member to equalizethe high and low pressure regions on opposite sides of the member.

Cavitation of the working fluid within the fluid ports or passages isanother problem relating to porting, particularly where the fluid isunder low pressure, as is the intake fluid of a pump. In conventionalhigh pressure hydraulic units of the radial piston type, the workingfluid is communicated to and from the unit in relatively small passagessurrounding the shaft. The shaft, or a coupled extension thereofrotating with the shaft, connects the passages through the fluid portsto the working chamber. All the structure defining the ports andpassages is generally between the axis of the shaft and the workingchambers. This necessarily results in a design wherein the passages arerelatively small, and the ports are quite limited in dimensions. Sinceat high operating speeds there is insufficient time to accelerate thelow pressure fluid through the small ports and passages without causingcavitation it has been necessary to pressurize the intake fluid of apump.

High pressure piston-type hydraulic units commonly operate at somespecific unchangeable volumetric displacement per cycle. This is adefinite drawback, since frequently it is desirable to vary thedisplacement per cycle for various power requirements, or for variouscyclic frequencies. However, the variable displacement high pressurehydraulic units available in the past generally have been quitecomplicated and lacked dependability for long periods of industrialapplications.

Accordingly, an object of this invention is to Provide a high pressurehydraulic pump or motor unit having a combination of design featuresthat eliminates all couples, or cocking moments, between the adjacentparts caused by the working fluid pressure. and that yields fluid filmscapable of supporting separated from each other the mating surfaces ofthe adjacent parts, regardless of the magnitude of the working pressure.

Another object of this invention is to provide a high pressure hydraulicpump or motor in which leakage of the working fluid between the high andlow pressure regions is minimized.

Another object is to provide a hydraulic unit in which each workingchamber is ported symmetrically to eliminate side thrust of its portcontrolling member.

Another object is to provide a high speed hydraulic pump in which thelow pressure fluid can be ported without cavitation.

Another object is to provide a high pressure hydraulic unit in which thevolumetric displacement per cycle can be adjusted.

Another object is to provide a hydraulic unit that is easily fabricatedwhile yet being dependable in operation.

The particular embodiments of this invention, both as to their structureand mode of operation, will be better understood by reference to thefollowing specification including the drawings forming a part thereofwherein:

FIG. 1 is an elevational view of an embodiment of the "hydraulic unitforming a part of this invention;

FIG. 2 is a section view taken on line 2-2 of FIG. 1;

FIG. 3 is an elevational view, partly in longitudinal section, as seenfrom line 33 of FIG. 2;

FIG. 4 is a perspective view of a cylinder member used in the hydraulicunit;

FIG. 5 is a perspective view of a piston member used in the hydraulicunit;

FIG. 6 is a perspective view of a guide block used in the hydraulicunit;

FIG. 7 is an elevational View of a manifold used in the hydraulic unit;

FIG. 8 is an elevational view as seen from the rear of FIG. 7;

FIG. 9 is an elevational view, partly in section, of a second embodimentof the hydraulic unit forming a part of the invention;

FIG. 10 is a sectional view taken on line 10-10 of FIG. 9;

FIG. 11 is an elevational view, partly in section, of a third embodimentof the hydraulic unit forming a part of this invention;

FIG. 12 is an enlarged view as seen from line 12-12 of FIG. 11;

FIG. 13 is an enlarged view as seen from line 13-43 of FIG. 11;

FIG. 14 is an elevational view of a slotted separating port plate usedin a fourth embodiment of this invention;

and

FIG. 15 is a sectional view taken on line 15-15 of FIG. 14.

In general, a hydraulic unit utilizing the teachings of this inventionincludes a stationary housing centrally supporting a rotatable shafthaving an eccentric thereon. The housing has concave pockets orchannels, extending transversely of the shaft, which. are open towardthe eccentric. A cylinder member is matably received in each pocket anddefines a central cylinder open towards the eccentric. A cruciformpiston is rotatably mounted on the eccentric and has radial arms each ofwhich is matably received in one of the cylinders. Upon rotation of theshaft each piston arm reciprocates within its cylinder to define avariable volume chamber, while each cylinder member simultaneouslyreciprocates within its pocket. Each variable volume chamber moves withits defining piston arm and cylinder member so that it is alwaysdisposed symmetrically thereof to eliminate reaction couplestherebetween. A restricted pass-age intercommunicates the fluid chamberand the interface of the moving and reaction members to establish apressurized supporting fiuid film therebetween. The housing hasperipherally located inlet and outlet ports associated with each fluidchamber that separately communicate with the chamber in certain operatepositions of the mating members. The mating members all mate onrelatively large surfaces supported spaced from each other on a film offluid pressurized from the working fluid.

Referring now to the drawings, and particularly to FIGS. 1, 2 and 3, apreferred embodiment includes a housing 10 having spaced port plates 48(FIG. 2) presenting mutually facing substantially parallel surfaces 14that sandwich four spaced shoe members 56 (FIG. 3). Each shoe member 50has an inwardly facing substantially straight surface 16 thereonextending between surfaces 14 of port plates 48. The opposite surfaces16 preferably are parallel to each other and disposed at angles 90 fromthe adjacent surfaces 16. The spaced surfaces 14 of port plates 48 andthe surfaces 16 of shoe members 59 define a generally enclosedrectangular cavity 17 within the housing 10. The cavity 17 may bedescribed as comprising four channels or pockets 12 defined by theconfronting surfaces 14 and each interconnecting surface 16 on the shoemembers 50.

Each pocket 12 matably receives a cylinder member 18, the cylindermember being slidable along a path generally parallel to theinterconnecting surface 16. Each cylinder member 18 (FIG. 4) isgenerally U-shaped, with spaced leg portions 24) defining mutuallyfacing straight parallel surfaces 22. The surfaces 22, along with thespaced surfaces 14 of the pocket 12, define a recess or cylinder 19 openinwardly of housing 10.

A single cruciform piston member 24 (FIGS. 3 and 5) is disposedcentrally of the cavity 17 and has four rigid arms 26 each mata-blyreceived in respective cylinder 19. The piston 24 is mounted centrallyon eccentric portion 28 of a shaft 30 rotatably supported by the housing10. As shaft 30 rotates piston 24 moves in a circular path about theaxis of the shaft without rotation about its own axis. The arms 26 ofpiston 24. mate with cylinder members 18 to move the cylinder memberrelative to the housing 10. Each piston arm 26 thereby reciprocateswithin its mating cylinder member 18 while simultaneously reciprocatingthe cylinder member along the respective surface 16. Since the oppositesurfaces 16 are parallel to each other, the opposite cylinder members 18move in the same direction at the same time. Each cylinder member 18 andits mating piston arm 26 defines a variable volume chamber 32.

The port plates 48 have two aligned inlet ports 34 and two alignedoutlet ports 36 associated with each chamber 32 and terminating atspaced surfaces 14. The edges of inlet ports 34 and outlet ports 36adjacent chamber 32 are preferably parallel to the confronting surfaces22 of cylinder member 18 and spaced apart a distance slightly greaterthan the distance between the surfaces 22. This slight overlap reducesdirect port-to-port leakage. The ports of each chamber 32 are positionedsymmetrically of the top dead center position so that both the inlet andoutlet ports are closed when the piston arm and cylinder member are inthe top dead center position. The length of the adjacent edges of theports are preferably as long as the stroke of piston arm 26.

As the shaft 39 rotates each cylinder member 18 reciprocates along theintermediate pocket surface 16, first to one side of its top dead centerposition, and then to the other side. The inlet ports 34 and outletports 36 are respectively uncovered or opened during each alternatehalf-revolution of shaft 30 by the lateral harmonic displacement of thecylinder member 18. The communicating openings between the respectiveports and each variable volume chamber 32 define generally rectangularslots extending the length of the chamber 32. At all positions of eachcylinder member 18 other than its top dead center positions and thesmall lateral displacement on both sides thereof corresponding to portoverlap, either the inlet ports 34 or the outlet ports 36 are at leastpartially open.

The aligned inlet ports 34 (FIG. 3) are all located clockwise of the topdead center positions, while the aligned outlet ports 36 are all locatedcounterclockwise of the top dead center positions. Consequently, theopposite chambers 32 are always out of phase with each other so that,while top chamber 32 (FIG. 3) is on the intake, the bottom chamber 180away is on the exhaust. Similarly the side chambers 32 are in oppositephases with respect to each other while being out of phase from the topand bottom chambers.

Manifolds 4th (FIGS. 2, 7 and 8) communicate with hydraulic fluidsources (not shown) to supply the ports. and chambers with a hydraulicfluid. Hydraulic fluid thus: is admitted to each chamber 32 on theinward stroke of piston arm 26 toward shaft 30 and discharged frorneagh.

chamber on the outward stroke of the piston arm away from the shaft.This operation is the same when the unit is used as a pump or as amotor.

The pressure of the fluid in each of the chambers 32 causes a force tobe exerted on the piston arm 26 and cylinder member 18. This force isexerted in a direction parallel to the longitudinal axis of piston arm26 and is equal to the product of the fluid pressure and the area of thepiston. Reaction to this force is absorbed by the eccentric 28 and shoemember 50. This reaction force acting on the effective moment arm of theeccentric 28 about the shaft 3% converts between pressure energy of thefluid and mechanical energy of the shaft.

Each fluid chamber 32 is always located symmetrically of a line disposedparallel to the direction of bias extending through the geometriccenters of the reaction surfaces of the fluid biased members 18 and 24mated with its respective reactive members 50 and 28. The entirereaction caused by the fluid in chamber 32 can be represented as beingtransmitted through these reaction centers. Since the reaction centersare also the geometric centers, the fiuid biased members are uniformlybiased against the reaction members 28 and 5!). Since there are nocouples caused by the chamber fluid pressure between each fluid biasedmember and its reaction member, there will be no couples between thefluid biased members 18 and 24 themselves. Thus none of the adjacentmating surfaces will be tilted relative to one another by the fluidpressures to affect line contact or to squeeze asymmetrically alubricating fluid film from between the adjacent members.

Two members having mated adjacent surfaces biased together by a forceapplied to the members can be supported separated from each other by alubricating fluid supplied continuously between the mated surfacesintermediate the edges thereof. Flow of the fluid to the edges of themated surfaces establishes a lubricating fluid film between thesurfaces. The roughness characteristics of the mated surfaces determinethe minimum thickness of the fluid film required to prevent directmetal-to-metal contact. The flow characteristics of the lubricatingfluid determine the fluid flow and pressure required to maintain thefluid film at the minimum thickness.

The film pressure varies from a maximum intermediate the mated surfacesto a minimum at the edges thereof. The leakage of the film past theedges of the mated surfaces Varies proportional to the supplied fluidpressure and to the cube of the film thickness. The load supportingcapacity of the film varies proportional to the supplied fluid pressureand to the film area. At balanced conditions, the integratedmathematical product of the film pressure acting on the mating areabetween the members will equal the biasing force to maintain the membersspaced from each other by the thickness of the film.

Since the fluid biasing force on members 18 and 24 against the reactionmembers 28 and 50 is proportional to the chamber pressure, it isdesirable that a proportionately high pressure supply the lubricatingfilm at the reaction area between the adjacent members. Passages 42(FIGS. 2 and 3) of restricted cross-section in each of the fluid biasedmembers 18 and 24 extend from the chamber 32 to the interface of theadjacent reaction members 28 and 50. A limited quantity of hydraulicfluid under a proportionately high pressure as that in chamber 32continuously flows from chamber 32 through each passage 42 to thereaction area between the members. This continuously flowing fluid underpressures proportional to the biasing force establishes the pressurizedlubricating film between the adjacent members.

In order to support the load without metal-to-metal contact, the averagepressure in the lubricating film multiplied by the film area must equalthe chamber pressure multiplied .by the piston area. The pressure in thechamber 32 is the sum of the pressure drops across the restriction 42and across the film. If the film thickness should increase, the filmresistance will decrease, thus increasing the fluid flow. The pressuredrop across the restriction will thus increase to reduce the averagefilm pressure. If the film thickness should decrease, the opposite willoccur, i.e., the flow will decrease, the pressure drop across therestriction will decrease, to increase the average film pressure. Thereis only one film thickness at which the average fil-m pressuremultiplied by the film area will equal the chamber pressure multipliedby the piston area. The film thickness will vary until this correctthickness is reached and balance is attained. If the film thicknessshould vary, for any reason, a net force will be exerted which willrestore the film thickness to the correct value.

In design, it has been established that the restriction should be chosenso that the balance occurs at a film thickness on the order of 0.0005inch. This is a much thicker film than might be needed fromconsiderations of surface roughness because with properly finishedsurfaces the roughness will be approximately 0.000005 inch. Thinnerfilms are not desirable because the force required to shear an oil filmvaries inversely with the film thick ness and thus the friction lossesincrease substantially as the film thickness is reduced.

For a positive balance and thus a stable support of loads, it has beenfound that the pressure drop across the restriction 42 should beone-third to one-half of the chamber pressure. The reaction areas arethen chosen to produce the desired film thickness. When the dimensionshave been chosen so that stable operation occurs, the film thicknesswill not change appreciably with cham: ber pressure. When the chamberpressure is increased, the pressure drop across the restriction and theaverage film pressure both will increase, since the sum of these willalways equal the chamber pressure. But the film thickness will remainnearly constant. This observed fact is extremely important because itpermits operation at very high working pressures without squeezing outthe oil film, thus avoiding metal-to-metal contact. Moreover, a stableoil film limits the high frictional losses which would otherwise occurwith very thin films.

With the design just described oil is supplied to the film only asneeded, thus limiting leakage and the resulting energy losses.

Metal-to-metal contact is avoided only when two conditions are met: (1)there is a stable film capable of supporting the load under alloperating conditions, and (2) the load is applied symmetrically withrespect to the film areas. Condition (1) is achieved as previouslydescribed. Condition (2) will require further explanation.

Referring to FIGURE 3, it will be noted that the useful force exerted bythe fluid in the chamber 32 can act only along a line parallel to thelongitudinal axis of the piston arm 26. This axis passes through thecenter of the eccentric 28 and symmetrically of the base of cylindermember 18, matable with shoe member 50. The force acting between theeccentric 28 and the shoe member 50 exerts a turning moment about thecenter of shaft 30 that is equal to the force multiplied by theeccentricity normal to the line of application of the force. As theeccentric 28 revolves, a point on the piston 26 moves in a circle whilethe cylinder member 18 oscillates along shoe member 50. The importantpoint is that the torque is always transmitted to the machine by meansof the centrally applied force between the moving eccentric 28 and thestationary shoe member 50 on a moment arm about shaft 30. There are nocouples, or cocking moments, exerted between the members which tend tocock the piston in the cylinder or which tend to tilt the cylindermember 18 with respect to the shoe member 50. In existing hydraulicunits these couples or cocking moments are present and often are verylarge in magnitude. Indeed, in many designs it is the only means oftransmitting torque to the frame of the machine and hence is equal tothe shaft torque. These couples and the resulting tilting moments resultin forces being applied which are asymmetrical with respect to the fluidfilm separating the members. Such asymmetrical application of forceinevitably destroys the balance previously described and results in linecontact between the metal surfaces.

Although the description and discussion have referred mainly to thefluid film between cylinder member 18 and shoe member St), the sameprinciples apply to the fluid film between the bore of the piston 24 andthe eccentric 28.

It is thus seen that the combination of balanced oil films and theelimination of cocking moments yields a major advance in the design ofhydraulic equipment.

Considering the construction of the unit more in detail, and referringspecifically to FIGS. 2 and 3, housing includes spaced bearing plates 46having inner sides which sandwich the outer sides of the above-mentionedspaced port plates 48. The inner sides of port plates 48 form thesubstantially flat parallel surfaces 14 of pockets 12. The port plates48 are maintained separated by the previously mentioned four shoemembers 50 and by four guide blocks 52 (FIG. 6). The guide blocks 52each have spaced guide surfaces 56 which face and are spaced from twoadjacent shoe member bearing surfaces 16. Bolts 58 and dowel pins 60extend through aligned openings in the bearing plates 46, port plates48, shoe members 50 and guide blocks 52 to secure them together rigidly.

Hubs 64 (FIG. 2) of bearing plates 46, and the port plates 4% havegenerally aligned central openings 66 extending completely through thehousing 10. The periphcries of openings 66 in bearing plates 46 snuglyreceive the outer races of bearing units 68. The shaft 30 extendsthrough the aligned openings 66 in the bearing plates and port platesand engages the inner races of bearing units 68. Bearing units 68preferably are self aligning double guide roller bearings whichadequately support the shaft 30 against both longitudinal and lateralforces. The eccentric 28 is a generally cylindrical section itnegralwith or keyed to shaft 30 intermediate the inner races of bearing units68. The eccentric 28 is disposed to rotate within the central openings66 of the port plates 48.

End plates 70 engage the hubs 64 of bearing plates 46 and have O-ringgaskets 71 disposed to ensure a sealed fit there'oetween. Bolts (notshown) extend through openings in the end plates 70 into threaded tapsin the hubs 64 to secure the two together. Each end plate 70 has acentral aperture 72 through which the shaft 3t) extends. Annular spacerelements 74 are tightly received on shaft 30 over interposed O-ringgaskets 75 and are rotatable as a unit with the shaft. Each spacer 74 isreceived in the end plate aperture 72 and rotatable therein in sealingrelationship with O-ring gasket 77. A threaded bore 76 through each endplate 70 to the interior or sump space of the unit provides forconnection to a hydraulic line (not shown).

Counterweights 78, keyed to shaft 30 adjacent end plates 70, equalizethe dynamic unbalance caused by the rotating piston 24 and reciprocatingcylinder members 18. Since all of the moving parts follow predeterminedpaths in parallel planes, dynamic balancing can be achieved by the twocounterweights 78, as is well known in the art. Cup-shaped covers 84)each having a central base opening 79 and a peripheral slot 81 covercounterweights 78 and end plates 70 and are secured to the end plates byappropriate means (not shown). Nuts 32 threaded onto the threadedportions of shaft 30 tightly engage interposed lock Washers 83 andcounterweights 78.

Thus the eccentric 28, inner races of the bearing units 68, the spacers'74, and counterweights 78 rotate as a unit with the shaft 30. It is tobe understood that there is suflicient axial clearance between piston 24and the bearing units 68 to permit relative rotationbetween the mem- 3bers Without binding or excessive wear. Keyed portions 84 of shaft 36project outwardly of end covers 86 for connection to a mechanical devicesuch as a driving motor (not shown) or to a driven unit (not shown)depending whether the unit is used as a pump or motor.

Annular oil jacket 36 surrounds the unit 10 at its midportion and issealed there-to by a pair of O-ring gaskets 87 disposed in annularnotches in the bearing plates 46. Port plates 48 preferably haveenlarged recesses 89 (FIG. 2) adjacent the ports remote from eachchamber 32 which reduce the hydraulic flow resistance through each port.Passages 91 in bearing plates 46 intercommunicate recesses 89 in theport plates 48 with a plurality of uniformly spaced counterboredopenings 93. The interior or sump space of the unit is completely sealedby the various O-ring gaskets. The only paths by which hydraulic fluidcan enter or leave the unit is through the threaded bores 76 in the endplates 70 and the openings 93 in bearing plates 46.

Manifolds 40 connect each chamber communicating openings 93 with theappropriate intake or exhaust hydraulic source (not shown). Eachmanifold 46 has an inner tube 88 and an outer tube (FIGS. 2 and 7)having communicating pipes 92 projecting from the tubes towards thehousing. A stepped flange 94 on the free end of pipe 92 is secured tohearing plate 46 against interposed O-ring gasket 95 and intothecounterbored opening 93. The manifolds 40 are identical so that adjacentpipes 92 are alternately connected to the inner and outer tubes 88 and99 to correspond to the alternate positioning of the inlet ports 34 andoutlet ports 36 about the unit. Consequently, as viewed in FIG. 2 theouter tube 9t) on the left manifold 40 and the inner tube 88 on theright manifold 40 are associated with the intake fluid, while inner tube88 on the left manifold and the outer tube 90 on the right manifold areassociated with the exhaust fluid. Passages 96 (FIGS. 1 and 7) extendfrom the intake and exhaust tubes in each manifold and secure Tconnections 10% between opposed flanges 93. The TS 100 each have athreaded bore 101 which receive a tube (not shown) respectivelyconnected to the intake and exhaust sources of fluid (not shown).

Consequently, any fluid directed to the intake T 100 is delivered toopposite sides of chamber 32 equally. The fluid is similarly exhaustedfrom opposite sides of chamber 32 through two manifolds having equalfluid pressures. This symmetric porting of each chamber eq'ualizes thehigh or low pressure regions on opposite sides of the cylinder member 18and piston arm 26 to eliminate biasing fluid forces tending to moreeither member towards one port plate 48 or the other.

It can be noted in FIGS. 2 and 3 that the fluid ports 34 and 36 andmanifolds 40 are located on the periphery of the unit adjacent thechambers 32. This arrangement permits the cross-section of both theports and manifolds to be large and of adequate size compared to themaximum volume of each chamber 32. Consequently, for each working strokeof any piston arm 26, the fluid in the manifold is displaced only ashort distance. Even when the unit is operating at a high speed and eachworking stroke takes only a fraction of a second, the fluid in manifold40 only needs to be accelerated slightly to keep up with the fullvolumetric displacement. This is particularly true since each chamber 32is supplied by two manifolds through two ports. This porting arrangementreduces cavitation to such an extent that high speed pumping operationsare generally possible without the necessity of having a pressurizedintake.

FIG. 4 shows one of the cylinder members 18 in perspective. Eachcylinder member 18 includes a generally U-shaped body portion havingopposed flat parallel surfaces 162 closely matable when assembled in thepocket 12 with the surfaces 14 of port plates 48. The base portion has astraight surface 104 partly defined by pro- 9 truding toes 106 havingflat surfaces 108 therein oppositely facing and extending parallel tosurface 104. The surface 104 mates with and reciprocates along bearingsurface 16 of the shoe member 50 while the toes 106 extend between theguide surfaces 56 of the guide blocks 52 and the bearing surface 16. Thedistance between guide surfaces 56 and bearing surface 16 is slightlygreater than the distance between the surface 104 and 108 to provide forfree cylinder member movement therebetween. Surfaces 56 and 108 areengageable only when the unit has stopped and gravity or residual fluidpressure between the surfaces 104 and 16 biases cylinder member 18 fromsurface 16.

Leg portions 20 define the mutually facing straight surfaces or faces22, previously mentioned, which extend parallel to each other andperpendicular to straight surface 104 symmetrically of its ends.

shallow groove or slot 116 extends along the intermediate portion ofbearing surface 104 spaced from the edges thereof and is interconnectedwith base surface 110 by aperture 118. An insert 120 secured within theaperture 118 has a through-bore of very small cross-section, generallyonly a few thousandths of an inch in diameter, which defines one of theabove-mentioned restricted passages 42.

' Generally C-shaped braces 122 fit over the free ends of legs 20 andengage flat surfaces 112 and ribs 114. Bolts 12,4 extend throughinterposed lock washers 126 and the apertures 125 in braces 122 intothreaded taps 123 in surface 112. The braces 122 constrain the free endsof the legs 20 from cantilever type deflection when hydraulic pressureis generated in chamber 32. Surfaces 22, which define two sides ofchamber 32, are located symmetrically from the ends of the cylindermember along the bearing surface 104. Thus fluid pressure in chamber 32will uniformly bias the cylinder member 18 against shoe member 50,causing no couples tending to establish line contact between theadjacent surfaces 16 and 104.

FIG. shows a preferred form of the cruciform piston 24, which includeshub 128 having central cylindrical through-bore 130. Arms 26 projectfrom hub 128 radially of the bore 130 and are spaced 90 apart. Each armis of uniform rectangular cross-section defined by flat parallelsurfaces 132 disposed perpendicular to the axis of said bore, straightparallel surfaces 134 disposed parallel to said axis, and end surface136. In the assembled position of the piston in the unit, surfaces 132are received between and mate with surfaces 14 of the port plates 48,while surfaces 134 are matable with surfaces 22 of cylinder member 18. Ashallow circumferential groove or slot 138 in the periphery ofthroughbore 130 extends over an arc of approximately 70 equidistantly ofthe center of each piston arm 26. Opening 140 in each piston arm 26extending between the slot 138 and surface 136, receives an insert 142therein having a through passage of very small cross-section whichdefines one of the previously mentioned restricted passages 42.

During operation of the unit, hydraulic fluid enters each chamber 32through inlet ports 34 and is discharged from the chamber through outletports 36. Regardless of whether the unit is used as a pump or motor, thefluid in each chamber 32 is under high pressure at some time during thecycle. The pressurized fluid acts on surfaces 110 and 136 of thecylinder member and piston, respectively, to bias them apart in thedirection of piston arm 26 and cylinder 19. Since each chamber 32 issymmetrically disposed with respect to the reaction areas of itsdefining moving members 18 and 24, the fluid biasing force produces nocouples between the members. Reaction of this biasing force is absorbedby shoe member 50 and by eccentric 28.

Each restricted passage 42 communicates limited quantitles of highpressure fluid from the chamber 32 to slots Base surface. 110 extendsbetween surfaces 22 and surfaces 102. A

116 and 138 in the interfaces between the fluid biased members 18 and 24and the reaction members 28 and 50. The hydraulic film varies inpressure somewhat linearly from its high at the slot to its low at theedges of the surface. Even though piston 24 is biased toward eccentric28, and the cylinder member 18 toward the shoe member 50, by thecontinuously changing resultant force from the changing fluid pressureswithin chamber 32, a supporting fluid film is maintained between themating adjacent surfaces. The reasons for this are two fold, since: (1)each chamber 32 communicates directly with the above-mentioned reactionareas to establish a proportionately high pressure supporting film, and(2) there are no couples between any of the mating surfaces caused bythe fluid pressure to reduce area contact to line contact. Consequentlyat all times the moving fluid biased members 18 and 24 are floated onhydraulic films adjacent the respective reaction members 50 and 28.

The fluid forced from chamber 32 past the mating surfaces 102 and 14 isdirected to the sump space. The fluid forced past the shoe member 50 andthe cylinder member 18 is directed in part to the peripheral region 146(FIG. 3) of the unit. The oil in the peripheral region 146 is circulatedin the oil jacket 86 and admitted to the sump space between the guideblocks 52 and the cylinder members 18. Slots 148 (FIG. 6) in the guideblocks decrease the flow resistance of the fluid to the sump space. Thefluid collected in the sump space is communicated through bores 76 inend plates 70 to the reservoir of the hydraulic system.

Since each cylinder member 18 and piston arm 26 are matable with thespaced surfaces 14 of the pocket, the flow path from the high pressureof the low pressure region is long and of high resistance. The leakagefrom each chamber 32 thus is minimized. However, any leakage is nottotally wasted as it lubricates the members for friction-free movementsrelative to each other.

FIGS. 9 and 10 show a second embodiment similar in part to that alreadydisclosed. Like components will thus be designated with the samereference numerals. The embodiment includes housing 10a having bearingplates 46a sandwiching a plurality of separating port plates 48a, shoemembers 50a and guide blocks 52a. Housing 10a. is secured together, andto supporting feet 154 by through bolts 58a. Shaft 30a extends throughaligned openings in the bearing plates 46a and is supported for rotationwithin bearing units 68a. Three cylindrical eccentric portions 28a arekeyed or otherwise formed adjacent each other on shaft 30a, the end orouter eccentrics being in phase, with respect to the longitudinal axisof the shaft, and 180 out of phase with the intermediate eccentric.

Cylinder members 18a reciprocate in pockets 12a defined by port plates48a and shoe members 50a. Three pistons 24a each having four equallyspaced radial arms 26a are respectively disposed on the eccentricportions 28a, with arms 26a matable with the cylinder members 18a.Rotation of shaft 30a. reciprocates the three pistons 24a relative eachmating cylinder member 1801 while simultaneously reciprocating thecylinder member along bearing surface 16a. The reciprocating piston arms26a and cylinder members 18a define the variable volume chambers 32a.Thus, each piston 24a and its mating cylinder members 18a, represent astage similar to that of the first embodiment.

Each chamber 32a. is symmetrically ported in the manner substantially asthat already disclosed. However, the inlet ports 34a and outlet ports36a communicate respectively with internal radial passages and 162 inport plates 48a. The passages 160 and 162 communicate respectively withspaced longitudinally extending channels 164 and 166 through the portplates 48a and shoe members 50a. Each of the channels 164 and 166extends to an annular inlet 168 or outlet 170 internal manifold in oneor the other of the bearing plates 46a. bores 174 and 176 in the bearingplates communicate Threaded I l'l respectively with the inlet and outletmanifolds 168 and 170 providing ready connection means to the hydraulicsources (not shown).

The inlet annular manifold 168 thus communicates with each longitudinalpassage 164 which in turn communicates with the inlet ports 34a throughthe radial passages 160. Similarly, the outlet annular manifold 1'70communicates with each outlet port 36a through longitudinal passages 166and radial passages 162.

Each reciprocating cylinder member 18a alternately covers and uncoversthe inlet and outlet ports for communicating the hydraulic source withthe defined chamber 3211.. As shown in FIG. 10, upper chambers 32a ofthe outer stages are On intake, while the lower chambers of the outerstages are on exhaust. Conversely the upper and lower chambers oftheintermediate stage are on ex haust and intake, respectively.

Preferably the piston arm areas of surfaces 136a of the outer stages areequal, with their combined areas being equal to the piston arm areas ofthe inner stage. Since the strokes of each stage are the same, the fluiddelivery and torque of the outer stages are equal to and 180 out ofphase with the inner stage. Also, since the opposite piston arms of theinner .andouter stages are simultaneously operating on the same phase ofthe cycle (eitherintake or exhaust), the opposed biasing forces of thestages do not appear as loads on the bearings 68a, but substantiallycancel each other. Similarly the unit is balanced dynamically since themass of the outer stages counteracts the mass of the inner stage.

FIGS. 11, 12 and 13 disclose a third embodiment which is particularlyadaptable as a variable displacement hydraulic unit. A pair of frames180 and 182 secured together by bolts 184clamp two adjacent housings 186and 188 snugly against one another. Shaft 30/) is rotatably mounted onhearing units 68b and has two adjacent eccentric portions 28b inpositional relationship 180 out of phase with respect to each other.Housing 186 is aligned with one eccentric 28b and is fixed rigidly tothe frame 180. Housing 188 is aligned with the other eccentric 23b andismovable about shaft 30b relative to the fixed housing 186. The movablehousing 188is rotated by hand wheel 190 fixed on shaft 191 throughmating worm gear 192 and annular rack 194 secured respectively to shaft191 and housing 188.

The housings include spaced separating plates 48b and 196', and 198 and200, respectively, which sandwich shoe members Stlb and guide blocks 52bto define the inwardly facing C-shaped pockets 12b. Cylinder members1811 and arms 26!) of piston 24b are matably disposed in the pockets andreciprocate relative to each other to define variable volume chambers32b. The pistons 24b in each giggising are actuated by eccentricportions 28b on shaft To simplify the disclosure of the fundamentaloperation'of the unit each stage is shown to have only two chambers 32b.It will be understood, however, that the preferred embodiment willinclude more than two chambers per stage, presumably four equally spacedchambers asshown in the first two embodiments.

The separating plate 481) of fixed housing 186 has an inlet port 34b andan outlet port 3612 associated with each chamber 32b, and is similar tothe port plates previously described. Separating plate 196 of fixedhousing 136 has shallow indentations or blind ports (not shown) alignedwith the inlet ports 34b and outlet ports 36b of plate 48b. The shallowindentations balance in part the low pressure region in the chambercaused by porting of the fluid. The separating plates 198 and 200 ofmoving housing 188 have no inlet and outlet ports therein, but haveopenings and slots to be discussed hereinafter.

The separating plates 196 and 198 have adjacent surfaces that aresubstantially identical. The mating surfaces have a series of separatelymatched slots 202 extending circularly about the shaft 3012 at givenradii each through an angle of approximately as shown in phantom in FIG.13. The matched slots of the plates overlap to form a continuous passagefrom one end of one slot through a maximum angle equal to the arc of thetwo matched slots, minus the overlap, or approximately Openings 204extend through each separating plate and communicate with the slots 202therein. The openings 204 are spaced 180 apart and at a commonradiusfrom the center of the plates to communicate the variable volumechambers 32!; of one stage with like or-corresponding chambers 32b ofthe other stage.

communicating passage with thecorresponding chamber 32b of the movablehousing 188. i

As shown in FIG. 13 the two housings are rotated an angle A relative toone another so thatthe intercom-. municated chambers are in other thanphase relationship. When angle A is equal to 0 the stagesare in phaseand the corresponding pistons of each stage move in the same directionat the same time relative to its mating. cylinder member. Thus, theintercommunicated chambers .32!) are on intake or on exhaust at the sametime. Consechambers completely. The reciprocating cylinder members ofthe stationary housing 186 control the porting to and from the chambersof both housings.

When the stages are in phase (when angle Ais equalto 0) the totalhydraulic flow to and from the unit isadditive and is equal to the sumof the intercommunicated chamber volumes. relative to each other andangle A becomes larger than 0, the stages are actuated inout-of-phaserelationship. The total fluid flow to and from the unit willthen 'be reduced. This is because the volume change of chambers 32binfixed housing 186 is partially counteracted by a different volumechange of its intercommunicated-cham-v bers 32b in moving housing 188for an incremental rotation of the shaft 30b.

When the two stages are rotated so thatangle A is equal to 180, thestages are in opposite phase relationship with respect to each other.The volume changes of the intercommunicated chambersare thensubstantially opposite each other for a given rotation of the shaft 3%.Consequently, the total volume to and fromthe units is effectivelyreducedto zero. The hydraulicfluid in the unit is surged back and forthbetweentheintercommunicated chambers in the stationary and movablehousings.

Thus, the resultant flow to and'from the unit can be varied as desiredfrom its maximum displacement (the sum of the two stages) when thestagesare in .phase to its minimum displacement (approximately zero whenthe stages are 180 out of phase.

FIGS. 14 and 15' show a separating plate, correspond-- ing to plate 198of FIG. 11, operable for a variable dis-- placement hydraulic unithaving four equally spaced chambers for each stage. The plate hasmatched slots 206 on two different radii and chamber communicatingopenings 208. Radial passages 210'between the larger radius slots 206and openings 208 align the openings 208' with the chambers 32b, whileyet not interfering with the separate independent action of each slot.Plug 212 closes the outer end of passage 210.

It is thus seen that the teachingsv of this invention have substantiallyeliminated the defects of prior hydraulic units. The fluid pressuresgenerated in the unit are transmitted through reaction centers of theyariouschamber defining members symmetrically of the members, thuseliminating couples between the members. The fluid biased members arefloated spaced from the reaction members on a continuous pressurizedfluid film. Each fluid chamber is. defined by mating members'having highresistance flow paths therebetween to minimum leakage.

Each chamber 32b of the stationary housing 186 thus has a continuousfluid As the housings are rotated Fluid porting of each chamber is ampleto eliminate cavitation. The various hydraulic units disclosed arereliable, while yet not prohibitive by construction cost or complexcomponents.

Various embodiments disclosed herein have been built to operate atspeeds up to 5,000 rpm. and the fluid pressures up to 5,000 p.s.i. Aunit smiliar to that described in FIG. 1 having 1" square piston armswith a /2 stroke has a total displacement of 2 cubic inches perrevolution. The flow rate is approximately gallons per minute at 125hydraulic horsepower. The unit weighs but pounds.

A unit as disclosed in FIG. 9 having intermediate stage piston ams /2"by /2" with the outer stage piston arms /z" x A" has approximately 40gallons per minute fluid flow with 120 hydraulic horsepower. The unitweighs approximately pounds.

While various specific embodiments have been shown, it will be obviousto those skilled in the art that many changes can be made withoutdeparting from the spirit of the invention. Thus, while the embodimentsshown included stages having two or four equally spaced chambers, manyother chamber combinations for each stage are possible. Thus a hydraulicunit having stages with three, five, six or even seven equally spacedchambers might be desirable. It is evident that with the greater numberof out-of-phase chambers in each stage, the fluid delivery and the shafttorque will be generally smoothed out. It is thus desired that theinvention herein disclosed be limited by the claims hereinafterfollowing.

What is claimed is:

1. A hydraulic pump or motor unit comprising a frame, two housingssecured by the frame adjacent each other and mating on mutually facingfiat surfaces, a shaft rotatably secured centrally of the housings andextending normal to the flat surfaces, eccentric means on the shaftaligned with the housings, each of the housings having a plurality ofcircumferentially spaced pockets defined in part by mutually facingopposite sides extending toward the eccentric means, a generallyU-shaped cylinder member matably received in each of the pockets so thatits leg portions along with the opposite sides of the pockets define acylinder open towards the eccentric means, each cylinder member beingmovable in its pocket along a path extending transversely of the shaft,a piston associated with each housing rotatably mounted centrally on theeccentric means and having radial arms projecting respectively towardthe pockets in the respective housing, said arms being matably receivedin the cylinders and recirpocal therein to define variable volumechambers, said arms adapted to simultaneously reciprocate the cylindermembers along their respective paths, one of the housings ha'ving inletand outlet ports associated with the chambers therein alternately openedby the cylinder members to communicate with the chambers, means tocommunicate hydraulic fluid to and from the respective ports, said flatmating surfaces having matched circular slots 5 therein to providecontinuous communication between the chambers of one housing and thecorresponding chambers of the other housing, and means to rotate thehousings relative to each other about the shaft to vary the relativephase relationships between communicating chambers to vary the flow ofhydraulic fluid to and from the unit. 2. A hydraulic pump or motor unitcomprising a frame, two housings secured by the frame adjacent oneanother, a shaft rotatable within the housings, ea-ch housing having twowalls spaced apart to define a cavity therebetween and the adjacentinner walls of the housings mating with one another along mutuallyfacing surfaces symmetrical of the shaft, means within each cavity inclose cooperating relationship with the housing walls thereof andmoveable by the shaft to define an expansible fluid chamber in eachhousing, port means in one of the housings for communicating a hydraulicfluid to the fluid chamber defined therein, the adjacent inner walls ofthe housings each having port means therein communicating with theseparate fluid chambers and further having paired circular slots formedalong the mutually facing surfaces and communicating with the respectiveport means operable to provide continuous communication between theseparate fluid chambers, and means to rotate the housings relative toone another on the mutually facing surfaces to phase the outputrelationship between the chambers.

3. A hydraulic pump or motor unit according to claim 2, wherein each ofthe circular slots extends through an angle of approximately so that thepaired slots to 35 gether can be extended through an angle of 4. Ahydraulic pump or motor unit according to claim 3, wherein each of thepaired slots is curved on a similar radius having its center at theshaft.

References Cited by the Examiner UNITED STATES PATENTS 2,747,516 5/1956Gastrow 103l6l 3,123,013 3/1964 Ganahl l03---37 FOREIGN PATENTS 479,5502/1938 Great Britain. 652,092 4/ 1 Great Britain.

SAMUEL LEVINE, Primary Examiner.

DONLEY J. STOCKING, Examiner.

R. M. VARGO, Assistant Examiner.

1. A HYDRAULIC PUMP OR MOTOR UNIT COMPRISING A FRAME, TWO HOUSINGSSECURED BY THE FRAME ADJACENT EACH OTHER AND MATING ON MUTUALLY FACINGFLAT SURFACES, A SHAFT ROTATABLY SECURED CENTRALLY OF THE HOUSINGS ANDEXTENDING NORMAL TO THE FLAT SURFACES, ECCENTRIC MEANS ON THE SHAFTALIGNED WITH THE HOUSINGS, EACH OF THE HOUSINGS HAVING A PLURALITY OFCIRCUMFERENTIALLY SPACED POCKETS DEFINED IN PART BY MUTUALLY FACINGOPPOSITE SIDES EXTENDING TOWARD THE ECCENTRIC MEANS, A GENERALLYU-SHAPED CYLINDER MEMBER MATABLY RECEIVED IN EACH OF THE POCKETS SO THATITS LEG PORTIONS ALONG WITH THE OPPOSITE SIDES OF THE POCKETS DEFINE ACYLINDER OPEN TOWARDS THE ECCENTRIC MEANS, EACH CYLINDER MEMBER BEINGMOVABLE IN ITS POCKET ALONG A PATH EXTENDING TRANSVERSELY OF THE SHAFT,A PISTON ASSOCIATED WITH EACH HOUSING ROTATABLY MOUNTED CENTRALLY ON THEECCENTRIC MEANS AND HAVING RADIAL ARMS PROJECTING RESPECTIVELY TOWARDTHE POCKETS IN THE RESPECTIVE HOUSING, SAID ARMS BEING MATABLY RECEIVEDIN THE CYLINDERS AND RECIPROCAL THEREIN TO DEFINE VARIABLE VOLUMECHAMBERS, SAID ARMS ADAPTED TO SIMULTANEOUSLY RECIPROCATE THE CYLINDERMEMBERS ALONG THEIR RESPECTIVE PATHS, ONE OF THE HOUSINGS HAVING INLETAND OUTLET PORTS ASSOCIATED WITH THE CHAMBERS THEREIN ALTERNATELY OPENEDBY THE CYLINDER MEMBERS TO COMMUNICATE WITH THE CHAMBERS, MEANS TOCOMMUNICATE HYDRAULIC FLUID TO AND FROM THE RESPECTIVE PORTS, SAID FLATMATING SURFACES HAVING MATCHED CIRCULAR SLOTS THEREIN TO PROVIDECONTINUOUS COMMUNICATION BETWEEN THE CHAMBERS OF ONE HOUSING AND THECORRESPONDING CHAMBERS OF THE OTHER HOUSING, AND MEANS TO ROTATE THEHOUSINGS RELATIVE TO EACH OTHER ABOUT THE SHAFT TO VARY THE RELATIVEPHASE RELATIONSHIPS BETWEEN COMMUNICATING CHAMBERS TO VARY THE FLOW OFHYDRAULIC FLUID TO AND FROM THE UNIT.